Arrangement for electric intercommunication



Jan. 24, 1939. RQCHQW 2,144,936

ARRANGEMENT FOR ELECTRIC INTERCOMMUNICATION Filed April 18, 1955 (zanyLow Fr'e fzzvezzi'an out in Bfatenteol .Fan. 24;, 1939 1-. PATET OFFlARRANGEMENT FOR ELECTRIC INTER- COMMUNICATION Hans litochow,

signor to C.

1 Claim.

The invention is concerned with a circuit arrangement for electricintercommunication between two stations. It is well known to provide forsuch purposes a switching device which is operated manually and in sucha manner that at each station the receiver is rendered inactive when thetransmitter is cut in. If the direction of intercommunication ischanged, then at both stations the switching must be effected manually.It has also been suggested to so improve these arrangements that theswitching is made with the aid of relays which are controlled byspeech, 1. e. the arrangement of relays is such that the receiver of thestation just speaking is switched by a relay energized by the speakingcurrents over an amplifier. Arrangements of this kind have thedisadvantage however that the relays must be very sensitive andaccurately adjusted in order to ensure a good intercommunication. Inaddition the relays must be slow releasing in order not to becomedeenergized during the short pauses intervening between the individualwords. This on the other hand however entails the disadvantage that atthe beginning of the speech certain parts thereof are cutoff by therelays, unless very complicated arrangements are employed, i. e.arrangements, which are not adapted for use with apparatus required tobe as light as possible.

The invention solves the problem by deriving from the speech currents acontinuous current which by displacing the grid potential acts to startthe transmitter and to stop the receiver.

The invention will be understood from the following description and beparticularly pointed the appended claim, reference being had to theaccompanying drawing which is a diagrammatic representation of anembodiment of the invention.

The microphone M is included in the input circuit of a low frequencyamplifier N. The output circuit of the low frequency amplifier isconnected with two transformers TS and TE. In the secondary circuits ofthese transformers bridge connections of the Graetz type are disposedwhich contain dry rectifiers of a well known kind. The rectifiedcurrents are passed over filter circuits S in order to control thetransmitter and receiver. The connection is such that the continuouscurrents shall produce in the transmitter and receiver actions which arethe reverse of each other. The transmitter when voice-actuated is so biBerlin-Tempelhof, Germany, as- Lorenz Aktiengesellsohaft, Berlin-Germany April 25, 1934 ased that the controlling transmitter which isquartz controlled, does not oscillate.

By the influence of speech is applied over resistance transmitter,transmitter control the final stage An action exactly the reverse ofthis is ner. produced in age renders that the rec a continuous voltageRl to the controlling this voltage being such that this a will be causedto oscillate and to working in push-pull manthe receiver. The continuousvoltthe bias of the receiver negative so eiver will be insensitive. Thisis attained by leading the continuous voltage to the resistance R2.Resistance R2 is included in the grid' circuit of all the stages. stageand the two The high frequency low frequency stages are how- 5 everadditionally biased by a battery Z, i. e. biased negatively,

whilst the grid of the audion is conto the resistance. When thearrangement is subjected to speech, the whole level of the circuit ofthe low receiver gets displaced. The output frequency amplifier N iscon- 20 nected not only with the transformers TS and TE but also with amodulation transformer of the the final stage is modulated in a nor withthe aid of grid potenti transformer TM, i. e. the transmitter. Here wellknown manthe method of modulating 25 als.

The additional current consumption for the controlling arrangementaccording to the in- The arrangement may for the resistances RI, R2 each30 require a current of 5 ma.

What is claimed is:

A two-way radio telephone station comprising a radio transmitterincluding a three-element n vacuum tube having grid biasing means fornormally preventing operation of said transmitter, a radio receiverincluding a three-element vacuum tube having grid biasing means normallyrendering said receiver operative, a connection between said vacuumtubes for maintaining the cathode elements of said tubes at the samepotential, a

source of low frequency currents for modulating said transmitter, andmeans including separate rectifier elements having their output circuitsdirectly connected respectively to said vacuum tubes 4 for supplyingdirect current from said low frequency current source ages of saidmitter oper inoperative.

to vary the biasing voltvacuum tubes to render said transative and torender said receiver HANS ROCHOW.

